1. Field of the Invention
The present invention relates to a display device in which a plurality of light-emitting tubes (also referred to as “a plasma light-emitting tube”, “a display tube”, “a gas discharge tube”, “a plasma discharge tube” and the like) are arranged in parallel to each other. More particularly, it relates to a display device constructed by arranging a plurality of light-emitting tubes in parallel comprising narrow tubes of a diameter of about 0.5 to 5 mm each having a phosphor layer provided and a discharge gas sealed inside for displaying optional images.
2. Description of the Related Art
A display device described in, for example, Japanese Unexamined Patent Publication No. 2000-315460 is well known as the above display device. In the display device, for obtaining a number of light-emitting points in a longitudinal direction of a light-emitting tube, a plurality of display electrode pairs are arranged on a substrate which supports the tubes, in a direction crossing the longitudinal direction of the tubes, an electrode forming face of the substrate is contacted with the tubes and voltage is applied to the plurality of the display electrode pairs.
However, in such a display device, it is difficult to manufacture light-emitting tubes having the same shape and performance, and the luminance (light-emitting luminance) of the tubes is not uniform due to variations caused when the tubes are manufactured. Thereby, when the light-emitting tubes are arranged in parallel to each other, non-uniformity of the luminance leads to irregular display of the display device.
Further, since the diameter of the light-emitting tubes is not microscopically uniform, areas where the display electrode pair formed on the substrate is in contact with each of the tubes are non-uniform. Therefore, variations of driving voltage will be caused by the non-uniformity described above, which leads to light-emission failures of the light-emitting points.